Fluorination process

Abstract

A liquid phase fluorination process for producing difluoromethane without corrosion is provided. In the process of this invention, methylene chloride and hydrogen fluoride are reacted in a reactor made of fluorinated polymer to produce a reaction product while a vaporized and superheated recycle stream of process reactants is fed into the reactor.

What is claimed is: 
     
       1. A process comprising the steps of: (a) reacting reactants comprising methylene chloride and hydrogen fluoride in the presence of an effective amount of a fluorination catalyst and in a reactor made of a fluorinated polymer to produce a reaction product; and   (b) distilling the reaction product in a first distillation column to produce a first column bottoms product that is recycled to the reactor and a first column overhead product comprising hydrogen chloride, difluoromethane, monochloromonofluoromethane, methylene chloride, and hydrogen fluoride;   (c) distilling the first column overhead product in a second distillation column to produce a second column bottoms product comprising monochloromonofluoromethane, methylene chloride, and hydrogen fluoride and a second column overhead product comprising difluoromethane and hydrogen chloride;   (d) vaporizing and superheating the second column bottoms product; and   (e) recycling the vaporized and superheated second column bottoms product to the reactor.   
     
     
       2. The process of claim 1 wherein the first and second column bottoms products are superheated to a temperature of about 100 to about 200° C. before being recycled to the reactor. 
     
     
       3. A process comprising the steps of: (a) reacting reactants comprising methylene chloride and hydrogen fluoride in the presence of an effective amount of a fluorination catalyst and in a reactor made of a fluorinated polymer to produce a reaction product; and   (b) distilling the reaction product in a first distillation column to produce a first column bottoms product that is recycled to the reactor and a first column overhead product comprising hydrogen chloride, difluoromethane, monochloromonofluoromethane, methylene chloride and hydrogen fluoride;   (c) distilling the first column overhead in a second distillation column to produce a second column bottoms product comprising difluoromethane, monochloromonofluoromethane, methylene chloride, and hydrogen fluoride and a second column overhead product comprising hydrogen chloride;   (d) distilling the second column bottoms product in a third distillation column to produce a third column bottoms product comprising monochloromonofluoromethane, methylene chloride, and hydrogen fluoride and a third column overhead product comprising difluoromethane;   (e) vaporizing and superheating the third column bottoms product; and   (f) recycling the vaporized and superheated third column bottoms product to the reactor.   
     
     
       4. The process of claim 3 wherein the first, second and third column bottoms products are superheated to a temperature of about 100 to 200° C. before being recycled to the reactor. 
     
     
       5. A process comprising the steps of: (a) reacting reactants comprising methylene chloride and hydrogen fluoride in a reactor made of a fluorinated polymer in the presence of a fluorination catalyst to produce a reaction product;   (b) distilling the reaction product in a distillation column to produce a column bottoms product comprising hydrogen fluoride, methylene chloride and monochloromonofluoromethane and a column overhead product comprising hydrogen chloride, difluoromethane, monochloromonofluoromethane, methylene chloride, and hydrogen fluoride;   (c) partially vaporizing the column bottoms product to produce a vapor portion and liquid portion;   (d) superheating the vapor portion; and   (e) recycling the superheated vapor portion and the liquid portion to the reactor.   
     
     
       6. A process comprising the steps of: (a) reacting reactants comprising methylene chloride and hydrogen fluoride in a reactor made of a fluorinated polymer in the presence of a fluorination catalyst to produce a reaction product,   (b) distilling the reaction product in a distillation column to produce a column bottoms product comprising hydrogen fluoride, methylene chloride and monochloromonofluoromethane and a column column overhead product comprising hydrogen chloride, difluoromethane, monochloromonofluoromethane, methylene chloride, and hydrogen fluoride;   (c) withdrawing a liquid sidestream from an intermediate part of the distillation column;   (d) vaporizing and superheating the liquid sidestream; and   (e) recycling the vaporized and superheated liquid sidestream to the reactor.   
     
     
       7. The process of claim 6 wherein the liquid sidestream is partially vaporized to produce a vapor portion and a liquid portion; the vapor portion is superheated; and the superheated vapor portion and the liquid portion are recycled to the reactor.